1. Field of the Invention
The present invention relates to a floor structure of a vehicle body for a motor vehicle and the like, particularly to a floor structure of a vehicle body to appropriately distribute a side collision load.
2. Description of the Related Art
A technique has been known as disclosed, for example, in JP-A-H06-107234 as a conventional technique for enhancing rigidity of a floor of a floor structure of a vehicle body including a floor panel for a motor vehicle and the like.
In the floor structure of the vehicle body according to the invention disclosed in JP-A-H06-107234, a floor panel 30, as shown in FIG. 11, has a structure including plural longitudinal beads 31 that extend along the longitudinal direction (rear and front directions) X of a vehicle (not shown in the drawing), and plural lateral beads 32 that extend along the lateral direction (right and left directions) Y of the vehicle (not shown in the drawing). The lateral beads 32 meet the longitudinal beads 31 vertically. The longitudinal beads 31 have a triangular cross section (not shown in the drawing), viewed in the longitudinal direction X of the vehicle. The lateral beads 32 have an approximately rectangular shape in a plan view and have continuous concaves and convexes including bases 32a and apexes 32b in a condition of crossing the longitudinal beads 31. Slope portion 32c are formed around each lateral bead 32, whereby the lateral beads 32 have such a figure that the apex 32b of the beads 32 projects higher above the apex 31b of the longitudinal 31.
In the conventional floor structure of the vehicle body, side sills are joined to the floor panel on both sides thereof, and lateral cross members are joined to the floor panel at the rear and the front thereof, or if necessary in the middle thereof, by welding. More considerations have recently been paid on enhancement in strength against a side collision and on how to distribute this side collision, so as to enhance strength and rigidity of a vehicle. For example, in an invention disclosed in JP-A-2004-314729, cross members provided in the approximately longitudinally middle part of the floor are continuously connected to each other through a tunnel section that is provided in the laterally middle part of the floor. Such a structure enhances strength against the side collision load and distributes this load.
However, when an external force from a side of the vehicle such as a collision load F is inputted, as shown in FIG. 11, the inputted load radially propagates over the floor panel 30 from a part at which the load has been inputted toward the direction indicated by an arrow D in FIG. 11.
In the conventional floor structure of the vehicle body, the longitudinal beads 31 vertically meet the lateral beads 32, and the lateral beads 32 have an approximately rectangular shape having a narrow portion at each corner (apex 32b) in a plan view. Consequently, the conventional floor structure has a disadvantage that deformation easily occurs at the narrow portion of the lateral beads 32 when the collision load F is inputted from the side of the vehicle.
Additionally, in the conventional floor structure of the vehicle body, a joint part between the side sill and the cross member is merely welded in a condition in which an end edge of the cross member abuts onto a side face of the side sill. Hence, the collision load F inputted into the side sill due to a side collision cannot propagate effectively to the cross members. Consequently, the conventional floor structure of the vehicle body has another disadvantage that deformation can easily occur at the joint part between the side sill and the cross member.
As a solution to prevent such deformations, it can be considered to increase a thickness of a component member or to provide a larger reinforcement member so as to enhance strength of the floor structure of the vehicle body. However, this solution increases weight of the vehicle body and may decrease the fuel economy. Therefore, there has been required a floor structure having high rigidity with a lighter weight.
To solve the above disadvantages, it is an object of the present invention to provide a floor structure of a vehicle body capable of enhancing rigidity against external force from a side of a vehicle body, and effectively propagating the external force to cross members.